Under the right conditions, farm chemicals can cause a pair of trousers to spontaneously combust if they are spilt on it and subjected to normal wear and abuse.

confirmed

The Build Team tried to ignite cotton denim pant swatches soaked in fertilizer, gun cotton solution, black powder, and the herbicide sodium chlorate using an open flame, radiant heat source, friction, and impact, but only the herbicide could ignite with sufficient energy under the above conditions (except for friction), and it was particularly reactive to impact. In a full-scale experiment using Buster, paramedics on-hand stated that Buster would most likely survive from the blast with only some burns.

(This myth comes from New Zealand in the early 1930s, where an epidemic of the myth had rampaged, injuring and even killing farmers. The culprit was a then-unknown chemical substance that farmers began using in large quantities at the time.)

You can “stick it to The Man” and get cheap uber-fuel efficiency with carburetor magnets.

busted

No change to fuel efficiency.

You can “stick it to The Man” and get cheap uber-fuel efficiency with acetone mixed with the gasoline.

busted

The acetone was less fuel efficient.

You can “stick it to The Man” and get cheap uber-fuel efficiency with “miracle carburetor.”

busted

Far less fuel efficient.

You can “stick it to The Man” and get cheap uber-fuel efficiency with a hydrogen fuel cell.

busted

The cell didn’t work with the car, and while the car did start unmodified when pure hydrogen was introduced, the hydrogen was also violently ignited soon afterwards, making it an unlikely – and expensive – alternative.

You can “stick it to The Man” and get cheap uber-fuel efficiency with used cooking oil, rather than regular fuel.

partly confirmed

Although there’s no word on damage to the engine from using used cooking oil, a diesel-fueled car did run on it. However, the MythBusters speculate that once this alternative fuel achieves a significant interest level among the public, used cooking oil will be hoarded as a salable commodity. The used cooking oil also did not quite fit the requirement of improved fuel efficiency, as it yielded approximately 10% less distance for an equivalent amount of diesel.